This invention relates to the examination of objects using a system of computed tomography (CT). CT is ordinarily used to examine the complete cross section of an object being studied, whether or not the entire object is of interest. When only an annular ring of the object is of interest, it is still necessary to scan the entire object, do the computations necessary for the entire object, and ignore the core of the object as not of interest.
U.S. Pat. No. 4,422,177 to Richard Mastronardi et al (1983) undertakes to do CT scanning of tubular objects such as rocket motors, but data concerning the entire cross-section is provided in a conventional manner to a computer for apparently conventional computations.
U.S. Pat. No. 4,725,963 to Morris Taylor et al (1988) discloses a CT system for inspecting cross-sections of tubes, but the scanning and computation do not allow the system to ignore the core of the tube.
U.S. Pat. No. 4,888,693 to Kwok C. Tam (1989) discloses a CT system for estimating the outer boundary or hull of an object, but the purpose of this system is not to examine the periphery of the object but to determine the position of the discontinuity between inside and outside the object.